#499 So many questions??

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#499 So many questions??

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Topics covered in this episode: PEP 824 brings ?? and ??= to Python for None handlingPython 3.15 gets a surprise RC3, and Python 3.10 reaches end of lifeasyncio.shieldPyxel: the retro game engine for PythonExtrasJokeWatch on YouTube About the show Sponsored by us! Support our work through: Our courses at Talk PythonConsulting from Six Feet Up Connect with the hosts Michael: Mastodon / BlueSky / X / LinkedInCalvin: Mastodon / BlueSky / X / LinkedInShow: Mastodon / BlueSky / X Join us on YouTube at pythonbytes.fm/live to be part of the audience. Usually Tuesday at 7am PT. Older video versions available there too. Finally, if you want an artisanal, hand-crafted digest of every week of the show notes in email form? Add your name and email to our friends of the show list, we'll never share it. Michael #1: PEP 824 brings ?? and ??= to Python for None handling PEP 824, a new draft from Marc Mueller sponsored by Guido van Rossum, proposes None-coalescing operators for Python 3.16. The ?? operator returns its left-hand side unless that value is None, and ??= assigns a fallback only when the target is None. It revives the long-deferred PEP 505 from over a decade ago, trimmed to just these two operators, with None-aware access split off into PEP 823. The goal is replacing verbose is None checks with something closer to or, but keyed on None instead of truthiness. Every Python codebase has piles of if x is None fallback code, and this is the first serious move in ten years to give it real syntax.user.age ?? "unknown" is like or but only falls back on None, so 0, "", and [] pass through instead of getting clobbereduser.name ??= "unknown" replaces the two-line check-then-assign pattern, with left-side subexpressions evaluated and cached exactly oncePrecedence sits between or and conditional expressions, matching JavaScript and C#, and ?? lands as a BoolOp in the AST next to and and orUnlike +=, ??= is a conditional assignment that skips the right side entirely, which is why it gets its own AST node rather than AugAssignStill draft status targeting 3.16, with a working reference implementation and an online demo to try, and it notably rejects a soft keyword like otherwise in favor of the familiar ??Discussion-worthy: the PEP answers the old objection that making None easier will proliferate its use, pointing out None is already everywhere and the status quo just produces uglier code # OG way user = db.get_user() city = None if user is not None: if user.address is not None: if user.address.city is not None: city = user.address.city # Michael's preferred way user = db.get_user() city = user?.address?.city Calvin #2: Python 3.15 gets a surprise RC3, and Python 3.10 reaches end of life The release team added a surprise third release candidate for Python 3.15 to fix last-minute lazy-import release blockers. They wanted time to test the fixes properly.That pushes the 3.15.0 final release from October 2 to October 9, 2026.RC3 has about 156 fixes from 82 contributors. The headline features are explicit lazy imports (PEP 810), the new frozendict (PEP 814) and sentinel (PEP 661) built-ins, and UTF-8 as the default encoding (PEP 686).No more ABI changes are coming, so library authors should be building 3.15 wheels now. uv 0.12.23 already added CPython 3.15.0rc3.On October 1, Python 3.10.22, 3.11.17, 3.12.15, 3.13.16 and 3.14.8 shipped together with nine common security fixes. They cover SSL validation, tarfile and zipfile handling, and urllib credentials.Python 3.10.22 is the final 3.10 release. After five years it gets no more security updates, so anyone still on 3.10 should upgrade.Python 3.13.16 is the last full maintenance release of 3.13, which now moves to security-only fixes. Only 3.13.16 and 3.14.8 have Windows and macOS installers, and the older releases are source-only.Python 3.11 gets security fixes through October 2027, and 3.12 through October 2028.A natural way to tie the two together: one version is nearly out the door and one is officially gone, and the same week is the time to test your code on 3.15 and move off 3.10. Michael #3: asyncio.shield Where async code can be cancelled In async Python, every await is a point where your coroutine can be stopped. If someone cancels the task, asyncio raises CancelledError at whichever await the coroutine is paused on, and nothing after that line runs. Quart does this on purpose. When the client disconnects, it cancels the request's task. From quart/asgi.py: elif message["type"] == "http.disconnect": self._disconnected = True request.body.disconnect() request_task.cancel() That's reasonable for a slow page nobody is waiting on anymore. It's a problem for a handler that writes to the database in two steps: await downloads.insert_one(event) # 1. log the download await totals.update_one(..., {'$inc': ...}) # 2. bump the episode's total A podcast app requests the MP3, gets what it needs, and hangs up. If it hangs up while step 2 is in flight, step 1 has already landed and...

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